Right: that is willpower, which means that by the article's findings, even if it worked for one person, telling other people that they "just have to do it" won't work if it already hasn't worked for them.
I have to do things I don't want to do all the time. Once I am in the mindset, it is trivial to just continue it. If I go to sleep, it is easily lost and takes hours to recover. Therefore, the easiest way to do it, is to simply not go to sleep and stay up for another two hours and ruin my sleep. It's very easy, zero willpower is needed. Willpower is completely overrated.
People who talk about willpower don't actually use it, they pretend that whatever they do requires a lot of willpower or demonstrates their willpower to make themselves look good.
Whats the difference between a mind trick, willpower, decision, and dedication?
Deciding that you will do something and not internally debating it IS willpower.